Kinematics and dynamics of deployable structures with scissor-like-elements based on screw theory

Because the deployable structures are complex multi-loop structures and methods of derivation which lead to simpler kinematic and dynamic equations of motion are the subject of research effort, the kinematics and dynamics of deployable structures with scissor-like-elements are presented based on screw theory and the principle of virtual work respectively. According to the geometric characteristic of the deployable structure examined, the basic structural unit is the common scissor-like-element（SLE）. First, a spatial deployable structure, comprised of three SLEs, is defined, and the constraint topology graph is obtained. The equations of motion are then derived based on screw theory and the geometric nature of scissor elements. Second, to develop the dynamics of the whole deployable structure, the local coordinates of the SLEs and the Jacobian matrices of the center of mass of the deployable structure are derived. Then, the equivalent forces are assembled and added in the equations of motion based on the principle of virtual work. Finally, dynamic behavior and unfolded process of the deployable structure are simulated. Its figures of velocity, acceleration and input torque are obtained based on the simulate results. Screw theory not only provides an efficient solution formulation and theory guidance for complex multi-closed loop deployable structures, but also extends the method to solve dynamics of deployable structures. As an efficient mathematical tool, the simper equations of motion are derived based on screw theory.     

Over-constraints and a unified mobility method for general spatial mechanisms Part 2: Application of the principle

The pre-research on mobility analysis presented a unified-mobility formula and a methodology based on reciprocal screw theory by HUANG, which focused on classical and modern parallel mechanisms. However its range of application needs to further extend to general multi-loop spatial mechanism. This kind of mechanism is not only more complex in structure but also with strong motion coupling among loops, making the mobility analysis even more complicated, and the relevant research has long been ignored. It is focused on how to apply the new principle for general spatial mechanism to those various multi-loop spatial mechanisms, and some new meaningful knowledge is further found. Several typical examples of the general multi-loop spatial mechanisms with motion couple even strong motion couple are considered. These spatial mechanisms include different closing way: over-constraint appearing in rigid closure, in movable closure, and in dynamic closure as well; these examples also include two different new methods to solve this kind of issue: the way to recognize over-constraints by analyzing relative movement between two connected links and by constructing a virtual loop to recognize over-constraints. In addition, over-constraint determination tabulation is brought to analyze the motion couple. The researches above are all based upon the screw theory. All these multi-loop spatial mechanisms with different kinds of structures can completely be solved by following the directions and examples, and the new mobility theory based on the screw theory is also proved to be valid. This study not only enriches and develops the theory and makes the theory more universal, but also has a special meaning for innovation in mechanical engineering.     

多环耦合机构末端件自由度计算的等效法

针对新型耦合机器人与常见并联机器人机构结构的迥异性,提出一种适应多环耦合机构末端件约束分析和自由度计算的新方法,此方法的主要思路是将多环耦合机构转化为并联机构。提出机构拆分原则,将连接输入和输出的部分拆分为多个独立单元体。应用螺旋理论逐一分析拆分出的单元体中各个耦合节点构件相对于机架的独立运动,将含耦合结构的独立单元体等效为一个串联分支,整个机构就等效为一个并联机构。分析等效并联机构各分支的运动螺旋系和约束螺旋系,采用二次反螺旋求得机构末端件的自由度。应用提出的等效替代法计算一个耦合机构的自由度,计算结果与原型一致,表明提出的新方法能够有效化简耦合机构的复杂性并正确求得自由度。     

A New Flexible Multibody Dynamics Analysis Methodology of Deployable Structures with Scissor-Like Elements

There are vast constraint equations in conventional dynamics analysis of deployable structures,which lead to differential-algebraic equations(DAEs) solved hard.To reduce the difficulty of solving and the amount of equations,a new flexible multibody dynamics analysis methodology of deployable structures with scissor-like elements(SLEs) is presented.Firstly,a precise model of a flexible bar of SLE is established by the higher order shear deformable beam element based on the absolute nodal coordinate formulation(ANCF),and the master/slave freedom method is used to obtain the dynamics equations of SLEs without constraint equations.Secondly,according to features of deployable structures,the specification matrix method(SMM) is proposed to eliminate the constraint equations among SLEs in the frame of ANCF.With this method,the inner and the boundary nodal coordinates of element characteristic matrices can be separated simply and efficiently,especially on condition that there are vast nodal coordinates.So the element characteristic matrices can be added end to end circularly.Thus,the dynamic model of deployable structure reduces dimension and can be assembled without any constraint equation.Next,a new iteration procedure for the generalized-a algorithm is presented to solve the ordinary differential equations(ODEs) of deployable structure.Finally,the proposed methodology is used to analyze the flexible multi-body dynamics of a planar linear array deployable structure based on three scissor-like elements.The simulation results show that flexibility has a significant influence on the deployment motion of the deployable structure.The proposed methodology indeed reduce the difficulty of solving and the amount of equations by eliminating redundant degrees of freedom and the constraint equations in scissor-like elements and among scissor-like elements.     

剪刀机构环形阵列可展结构的运动学与动力学研究

通过分析剪刀单元之间几何参数的关系,得到单元尺寸和单元数量与展开和收拢半径之间的约束条件;针对可展结构的组成特点,提出将单元机构法与运动影响系数法相结合,建立可展结构的运动学分析方法;将运动影响系数法与虚功原理相结合,形成了可展结构的动力学分析方法。通过算例证实了所建立的运动学和动力学分析方法的有效性。     

2Z-V型电动潜油螺杆泵采油系统用行星减速器优化设计

电动潜油螺杆泵采油系统(ESPCPS)的设计关键是要解决螺杆泵低转速、高扭矩的动力输入要求,研究实验结果发现机械减速器是整个机组系统的难点所在。根据胜利油田某油井工况对电动潜油螺杆泵采油系统用减速器的设计要求,采用2Z-V型少齿差行星齿轮传动进行优化设计。根据所建立的数学模型,选用可靠性高、搜索速度较快的分层网络法进行寻优,性能参数良好、优化效果明显。首次提出了潜油螺杆泵减速器综合性能系数R,解决了不同机组、不同工况下、不同结构潜油螺杆泵减速器的性能比较问题。     

基于FIS理论的Myard环形组网机构运动学分析

为揭示折展机构连续与瞬时运动的本质与代数关联,将有限瞬时旋量理论（FIS理论）应用于一类过约束折展机构的分析中,提出包括折展单元及其组网机构的运动学分析方法。首先介绍了FIS理论的基本原理、Myard机构和Myard环形组网机构的组成原理。其次对于Myard机构,通过选定合适的初始位形,以构建有限旋量闭环方程的方式解决了折展单元的关节运动参数映射,基于旋量三角积与螺旋运动的定义提出了基于有限旋量的轨迹求解方法,随后由有限与瞬时旋量的微分映射关系得到Myard机构的速度模型。在此基础上,结合参数化的等效广义副将3-Myard环形组网机构简化为单闭环机构,以求解机构的参数映射关系,随后借助与Myard机构相同的分析流程便得到组网机构的位移与速度模型。提出折展单元及其环形组网机构的关节参数映射、运动轨迹和速度模型的分析方法,丰富了折展机构的运动学分析理论,为解决折展单元及其组网机构的运动学分析问题提供了新选择。     

Over-constraint and a Unified Mobility Method for General Spatial Mechanisms Part 1: Essential Principle

Compared with the parallel mechanisms, the mobility analysis of the general multi-loop spatial mechanisms(GMSMs) is more difficult to obtain correct results. The reason is that its multi-loop is formed through several times of closings and there also exists motion coupling even strong coupling, where the over-constraints are concealed. However, the mobility analysis for this kind of mechanisms has been paid few attentions. A new systemic methodology for analyzing mobility is proposed for GMSMs also based on the screw theory. The key issue for mobility analysis is to recognize the over-constraint. Firstly, three theorems are given and point out: the reason and site of over-constraint occurrence, calculating the number of over-constraints by the screw theory, and how to analyze the over-constraints for a single-loop mechanism as well. Then, three closing forms for GMSMs are proposed including rigid closure, movable closure and dynamic closure, and for the three different forms the different analysis methods are also given. Especially, for the most difficult issue of GMSMs with the multi-loop closure in many times and the inevitable motion coupling, two important methods are proposed: "recognizing over-constraints by analyzing relative movement" and "recognizing over-constraints by virtual loop". The two methods are well used to solve the issue. Above-mentioned principles are not only systematic and effective but also unified. They provide a theoretical basis for the general multi-loop spatial mechanisms.     

网状可展开天线反射面精度调整技术研究

给出了改进型周边构架式空间网状可展开天线的具体结构方案,利用权因子法对辅助牵引面式网面精度调整技术进行了理论分析及调整方法研究。给出了网面精度调整的基本理论、公式以及调整步骤,在此基础上提出了型面精度优化的数学模型,并利用单纯形法进行了优化。利用ANSYS软件建立了相应的反射面精度调整模型,并进行了调整计算;证明了所提出的方法是正确性及所给天线的结构方案的合理性。     

折纸衍生空间可展结构研究回顾与展望刍议

作为起源于中国,发展于日本的传统手工艺,折纸由于其可以实现二维与三维结构之间形态高效转换的特性,近年来受到了科研人员与工程人员广泛的关注,为空间可展结构的创新研究提供了新的思路。对学界与工程界针对一维、二维、三维折纸衍生可展结构的研究现状进行了阐述,指出后续研究应关注的刚性平面载荷高效折展、柔性结构管理、非欧几里得折纸理论、驱动设计与动力学、重力卸载与试验考核、与其他折展机构的综合等六个问题。     

A quadrilateral mesh generating method using mean value interpolation

Although commonly used for meshing, sub-mapping method is frequently bothered by its unstable region segmentation process. Although region segmentation can be avoided with the help of recognized models, the existing algorithms of obtaining recognized models are still flawed. In order to obtain accurate recognized models and high meshing quality, a quadrilateral mesh generation method is proposed on basis of mean value interpolation. Firstly, computational coordinates of inner loop vertices are determined by mean value interpolation according to regularization result of outer loop. Secondly, under the barycenter superposition principle, surface’s recognized model is obtained by use of regularization result of inner loops. Finally, facial mesh is generated via solving equations. Experiments are carried out to testify feasibility, advantage and stability of the proposed method. The results manifest that the proposed method is able to guarantee meshing quality and is applicable for quadrilateral mesh generation of multi-loop surfaces.     

基于蜘蛛网结构的伞状可展机构设计与分析

根据蜘蛛网结构的几何特点,建立了蜘蛛网的结构简化映射模型。在此基础上,以平面四杆曲柄滑块机构为可展单元提出了一种新型伞状可展机构。利用ANSYS Workbench软件对模型进行静力学分析与优化,给出了蜘蛛圆网结构模型中捕丝间距的最佳比例关系;同时,建立了蜘蛛网刚架模型的刚度矩阵,利用矩阵位移法给出了捕丝间的最优夹角。基于捕丝间距的最佳比例和捕丝最优夹角,提出了受力性能最佳的伞状可展机构,并对其静力学性能进行了仿真分析。结果表明：基于蜘蛛网结构模型优化后的伞状可展机构强度性能得到提升。最后,设计制造了展开直径为1.2 m的可展机构模型,并对其运动过程进行模拟,验证了模型展开与收拢过程的有效性。     

井下V形金属密封环密封性能研究

提出一种适用于井下复杂环境的V形金属密封环,利用压力密封装置模拟40 MPa压差工作环境,研究V形金属密封环在井下流量控制阀中的密封性能。将V形环的力学模型分解为圆筒过盈配合与悬臂梁力学模型进行理论分析,得出密封接触面的应力计算公式,并利用ABAQUS进行仿真验证。建立V形环两种密封面(曲面与平面)的轴对称模型,分析密封环在40 MPa压差下,不同过盈量与倾角对密封性能的影响,并对比2种结构的性能。结果表明,在满足密封性能的前提下,平面密封结构的过盈量取值范围更广,并且在相同结构参数时的接触应力大于曲面密封。确定平面密封结构过盈量与倾角的取值范围,为井下流量控制阀中V形金属密封环的设计提供了参考,应力计算公式也为密封环的设计提供了一个初步的接触面应力。     

可展开固体反射面机构设计及运动学分析

针对传统固体反射面机构主反射面型面精度和收拢率较低的问题,设计了一种可展开固体反射面机构。首先,提出4种固体反射面机构可展单元构型并对其机构自由度进行分析,对比分析构型方案优缺点确定构型方案4作为可展单元基础构型,并对其结构和展开原理进行详细设计。通过D-H坐标变换建立该机构可展单元的运动学模型,根据几何约束条件建立机构位置矢量方程,利用向量封闭投影法解出各回转角间的关系,结合MATLAB软件编程对机构的位置、速度和加速度进行分析。应用ADAMS软件建立机构仿真模型,验证了机构运动学分析的正确性。最后根据机构中回转角的限制条件和结构尺寸关系,分析回转角和结构尺寸对可展开固体反射面机构收拢率的影响,确定2.2m可展开固体反射面机构的回转角和旋转角分别为78°和30°,中心圆盘半径、铰支座一孔纵向尺寸、切换连杆横向尺寸、纵向尺寸分别为245,8,40,18mm,收拢率为0.326,从而为可展开固体反射面机构的设计提供参考。     

空间充气硬化管成型工艺研究

充气硬化管是一种最基本的空间可展开结构,本文以7 m长的充气硬化管为研究对象,分析充气硬化管的结构特点和技术要求,通过对管壁材料、胶接方案、胶接工装、胶粘剂等成型工艺中的主要影响因素分别进行研究,摸索出一整套充气硬化管成型工艺路线,并且制造出实物样件,其性能满足结构设计要求。     

剪式机构阵列可展结构的静力学分析方法与应用研究

针对大型可展结构提出了一种新的结构静力学分析方法,克服了常规有限元方法在进行大型可展结构分析时计算量大、计算耗时长等缺点。首先建立了剪式单元机构的刚度矩阵,组装得到整体结构的刚度矩阵和有限元方程;然后通过等价变形,将总刚度矩阵表示成循环矩阵,有限元方程表示成离散卷积的形式;最后采用一种新的方法求解了卷积形式的平衡方程,得到了各铰链点的位移和约束力,提高了计算效率。     

基于BP神经网络与瞬态响应分析的电路故障诊断技术

论文研究了基于模式识别原理的人工神经网络电路故障诊断方法,结合仿真技术,应用瞬态响应分析把数模混合信号电路中数字电路部分与模拟电路部分统一进行诊断,探讨了模拟电路和数字电路特性相差太大难于诊断的问题。针对具体电路,利用MATLAB神经网络工具箱对电路进行仿真,结果表明,利用所提出的实现方法对模拟及数模混合电路进行了较准确的诊断,达到了预期的目的。     

Type Synthesis of Lower Mobility Parallel Mechanisms: A Review

Type synthesis of mechanisms aims to systematically determine all possible structures for a specific mobility requirement. Numerous methods based on di erent theories were proposed for type synthesis of lower mobility parallel mechanisms in past decades. However, there does not exist a comprehensive review on these approaches. Therefore, the goal of this paper is to give such a review, classifying the approaches proposed in the literature into three groups, namely, motion-based methods, constraint-based methods, and other methods. The motion-based methods include the Lie group based method, the GF set method, the linear transformation method, the POC set method,and the finite screw method. The constraint-based methods involve the screw theory-based method, the virtual chain method, the method based on Grassmann line geometry and line graphs, and the motion constraint generator method. Other methods contain the enumeration approach based on the general CGK mobility formula and the graph theory method. Upon thoroughly analyzing the characteristics and/or limitations of each method, this review provides a well reference to help researchers find an e ective synthesis method for innovative design and further scientific investigations for mechanisms.     

平行多回路机器人机构的瞬时螺旋运动

本文分析了6自由度平行多回路机器人机构的瞬时螺旋运动,建立起6个输入运动与机器人端执行器或机构中其他构件的瞬时运动关系的显表达式。所有导出的公式十分简明,便于应用,文章后部还将这种方法推广到一般空间非平行多回路机构。